In a large saucepan, combine the zucchini, water, onion, bouillon and seasoned salt. Bring to a boil. Reduce heat; cover and simmer for 5 minutes or until zucchini is tender. Cool slightly. In a blender, cover and process soup in batches until pureed. Return all to the pan. Add milk and butter; cook and stir until better is melted. Serve immediately or transfer to a freezer container. May be frozen for up to 3 months. To use frozen soup: Thaw in the refrigerator overnight. Transfer to a large saucepan. Cook and stir over medium heat until heated through.